(1) Background: Despite increasing recognition of immune checkpoint inhibitors (ICIs) and kidney immune-related adverse events (IRAEs), no large-sample studies have assessed the pathological characteristics and outcomes of biopsy-proven kidney IRAEs. (2) Methods: We comprehensively searched PubMed, Embase, Web of Science, and Cochrane for case reports, case series, and cohort studies for patients with biopsy-proven kidney IRAEs. All data were used to describe pathological characteristics and outcomes, and individual-level data from case reports and case series were pooled to analyze risk factors associated with different pathologies and prognoses. (3) Results: In total, 384 patients from 127 studies were enrolled. Most patients were treated with PD-1/PD-L1 inhibitors (76%), and 95% presented with acute kidney disease (AKD). Acute tubulointerstitial nephritis/acute interstitial nephritis (ATIN/AIN) was the most common pathologic type (72%). Most patients (89%) received steroid therapy, and 14% (42/292) required RRT. Among AKD patients, 17% (48/287) had no kidney recovery. Analyses of pooled individual-level data from 221 patients revealed that male sex, older age, and proton pump inhibitor (PPI) exposure were associated with ICI-associated ATIN/AIN. Patients with glomerular injury had an increased risk of tumor progression (OR 2.975; 95% CI, 1.176, 7.527; p = 0.021), and ATIN/AIN posed a decreased risk of death (OR 0.164; 95% CI, 0.057, 0.473; p = 0.001). (4) Conclusions: We provide the first systematic review of biopsy-proven ICI-kidney IRAEs of interest to clinicians. Oncologists and nephrologists should consider obtaining a kidney biopsy when clinically indicated.

Acute kidney injury (AKI) is a severe postoperative complication in patients undergoing major surgery. Proton pump inhibitors (PPIs) are used preoperatively as prophylaxis for postoperative gastrointestinal bleeding. Whether preoperative PPI use is associated with an increased risk of postoperative AKI remains uncertain. This retrospective cohort study used electronic medical records from the clinical data warehouse of Peking University First Hospital to screen all adult hospitalizations undergoing major surgery between 1 January 2018 and 31 December 2020. Exposure was preoperative PPI use, defined as PPI use within 7 days before major surgery. The primary outcome was postoperative AKI, defined as AKI occurring within 7 days after major surgery; secondary outcomes included in-hospital AKI and in-hospital mortality. A total of 21,533 patients were included in the study (mean [SD] age, 57.8 [15.0] years; 51.2% male), of which 944 (4.4%) were prescribed PPI within 7 days before major surgery (PPI users). Overall, 72 PPI users (7.6%) and 356 non-users (1.7%) developed postoperative AKI. After adjustment, preoperative PPI use was associated with an increased risk of postoperative AKI (adjusted OR, 1.47; 95% CI, 1.04-2.07) and in-hospital AKI (adjusted OR, 1.41; 95% CI, 1.03-1.94). Moreover, subgroup analyses showed that the risk of PPI on postoperative AKI was amplified by the concomitant use of non-steroidal anti-inflammatory drugs or diuretics. No significant difference was observed between preoperative PPI use and in-hospital mortality in the fully adjusted model (adjusted OR 1.63; 95% CI, 0.55-4.85). Preoperative PPI use was associated with an increased risk of AKI in patients undergoing major surgery. This risk may be enhanced by the concomitant use of other nephrotoxic drugs. Clinicians should weigh the pros and cons before initiating PPI prophylaxis.

Although not recommended for potential risk of worsening kidney dysfunction, continuation of renin-angiotensin aldosterone system inhibitor (RAASi) during an episode of acute kidney injury (AKI) is not rare in clinical practice, and the risk-benefit ratio for RAASi therapy should always be carefully evaluated. Limited data exists regarding the reasons for RAASi continuation during the acute course of AKI and its impact on kidney and overall outcomes. This retrospective study used electronic medical records from the clinical data warehouse of Peking University First Hospital to screen all adult admissions who developed AKI during hospitalization and were prescribed RAASi within 48 h prior to AKI onset between 1 January 2018 and 31 December 2020. Patients were further divided into RAASi discontinuers and continuers based on whether RAASi was withdrawn within 48 h after AKI onset. The primary outcome was non-recovery from AKI at discharge; the secondary outcomes were failure of full recovery from AKI and in-hospital mortality. A total of 321 patients were prescribed RAASi within 48 h prior to AKI onset, of which RAASi therapy was continued in 196 (61.1%) cases (RAASi continuers). Under-recognition of AKI was considered the main reason for the continuation of RAASi (143 cases, 72.9%), followed by the exclusion of RAASi as the culprit drug (31 cases, 15.8%), strong indications for RAASi (20 cases, 10.2%) and transient AKI (18 cases, 6.6%). The non-recovery rates were 58.6% and 29.6% in RAASi continuers and discontinuers, respectively. After fully adjustment, RAASi continuation was associated with an increased risk of non-recovery (RR, 1.727; 95% CI 1.179, 2.588) and failure of full recovery from AKI (RR, 1.427; 95% CI 1.062, 1.938) at discharge. A non-significant association was observed between RAASi continuation and in-hospital mortality in both unadjusted and adjusted model. Under-recognition of AKI was predominant and might be the main reason for continuing RAASi after AKI onset. Continuation of RAASi during an AKI episode was associated with poor kidney recovery in the short term. Timely recognition of AKI should be improved, and a dynamic risk-benefit ratio evaluation for RAASi is required to achieve optimal management.